This invention relates to a disc drive control device for controlling a disc drive unit such as a hard disc or the like, and particularly a control device suitable for a portable information processing device such as a lap top computer.
Lap top computers conventionally employ external memory devices such as, for example, floppy disc. More recently, hard disc drives have appeared in such computers to give greater storage.
Such a hard disc drive is generally provided with a built in disc controller which, when it receives a disc access demand from a host, controls positioning of the read/write head on the disc and the reading-out or writing-to a medium.
According to the prior art, upon completion of reading or writing in the data area of the hard disc, the head remains positioned over the cylinder where the reading or writing was done. When the host demands a further access, the head is moved to the cylinder containing the desired data, or to which data is to be written.
While the power source remains connected to the hard disc, the head is maintained out of contact with the hard disc due to rotation of the hard disc. When the power supply is cut off, rotation of the hard disc ceases, and the head comes into contact with the data area or the hard disc. Shaking of vibration occurring while the head is in contact the data area may injure the recording medium, thereby causing loss of data.
The problem is particularly severe in the case of a lap top computer, wherein the importance of mobility greatly increases the risk of damaging recorded data.